Showers are used in the papermaking industry to condition felt or wire fabrics. One such fabric conditioning application is where a flood of water or other liquid under low pressure is supplied to the felt surface to flush dirt particles from the felt and to neutralize wet streaks. A second conditioning application is where water is sprayed under pressure onto a felt in order to actually dislodge dirt particles from the fiber/yarn structure and to resist compaction. This requires intermittent use.
Shower systems are provided today which combine both purging and spraying and nozzles are available such as that disclosed in U.S. Pat. No. 2,803,499; U.S. Pat. No. 2,954,170; and U.S. Pat. No. 3,990,637 which perform this dual function. In nozzles of this type two positions of operation are utilized. One position is a purging position and the other position is a spray position.
While the systems as disclosed in the above patents provide many advantages there is still one difficulty in the dual type of nozzle system under consideration which clearly requires an improvement. It is well known that to form a good spray pattern, there must be an adequate supply of water presented to the orifice. This can be done by having a large hole through the piston to form a reservoir. The problem with having a large hole through the piston is, when the nozzle goes on purge, there is a large increase in volume discharged through the nozzles.
A single pumping system cannot handle high pump pressure of around 300 to 400 psi with low flows and also handle high flows at low or around 25 psi.
Competitive showers and systems that have spring loaded nozzles work on a secondary supply system. Water supply is valved off enough to reduce shower water pressure to cause the nozzles to open and yet hold the pump pressure up on its pressure curve. What is needed then is a second system to supply volume for purging and enough pressure to close the nozzles so the high pressure pump can again supply the showers.